This invention relates to a variable speed apparatus for performing variable speed control of an induction motor.
FIG. 7 is a diagram showing a configuration of a conventional variable speed apparatus. In the drawing, numeral 20 is a variable speed apparatus, and numeral 21 is a converter part for converting AC electric power R, S, T from a three-phase AC power source into DC electric power, and numeral 22 is a smoothing capacitor for smoothing a DC voltage converted by the converter part 21, and numeral 23 is an inverter part for converting the DC electric power into AC electric power U, V, W of a variable frequency, a variable voltage. Also, numeral 24 is a storage part for storing data such as adjustable speed patterns of linear adjustable speed or S-shaped curve adjustable speed, etc. set by parameters, an adjustable speed reference frequency fstd, a frequency fmin at the time of low speed, reference acceleration time ta1 for accelerating from 0 Hz to the adjustable speed reference frequency fstd, reference deceleration time td1 for decelerating from the adjustable speed reference frequency fstd to the frequency fmin at the time of low speed, and numeral 25 is a control part for controlling the inverter part 23 based on various data set in the storage part 24 by a start command, a deceleration stop command, etc. and numeral 26 is a motor. Here, the adjustable speed reference frequency fstd is a frequency based in order to calculate a gradient of adjustable speed, and the maximum value of an operating frequency is normally set.
In the conventional variable speed apparatus 20, the adjustable speed patterns, the reference acceleration time ta1, the adjustable speed reference frequency fstd, the reference deceleration time td1, the frequency fmin at the time of low speed, etc. are preset by parameters, and when a start command is inputted, acceleration is performed by the reference acceleration time ta1 to an operating frequency (=adjustable speed reference frequency fstd) commanded by the adjustable speed patterns set, and constant speed operation is performed at the operating frequency (=adjustable speed reference frequency fstd). During the constant speed operation, when a deceleration stop command is inputted, there is performed variable speed control in which deceleration is performed by the reference deceleration time td1 to the frequency fmin at the time of low speed by the adjustable speed patterns set and constant speed operation is performed at the frequency fmin at the time of low speed and then a deceleration stop is made by an input of a stop command. Among these, the reference acceleration time ta1 is set as reference acceleration time for accelerating from 0 Hz to the adjustable speed reference frequency fstd and also, the reference deceleration time td1 is set as reference deceleration time for decelerating from the adjustable speed reference frequency fstd to the frequency fmin at the time of low speed. When an operating frequency targeted at the time of acceleration is different from the adjustable speed reference frequency fstd, acceleration time ta2 is calculated by multiplying the reference acceleration time ta1 by a ratio between the operating frequency targeted at the time of acceleration and the adjustable speed reference frequency fstd, and also when an operating frequency at the time of input of a deceleration stop command is different from the adjustable speed reference frequency fstd, deceleration time td2 is calculated by multiplying the reference deceleration time td1 by a ratio between the operating frequency at the time of input of a deceleration stop command and the adjustable speed reference frequency fstd.
FIG. 8 is a diagram showing a control method of the conventional variable speed apparatus, and FIG. 8(a) shows an operation pattern, and FIG. 8(b) shows a state of a deceleration stop command/stop command. In the drawing, fstd is an adjustable speed reference frequency, and fmin is a frequency at the time of low speed, and td1 is reference deceleration time for decelerating from the adjustable speed reference frequency fstd to the frequency fmin at the time of low speed, and B is an operation pattern of the case that a deceleration stop command is inputted during operation at the adjustable speed reference frequency fstd, and C is an operation pattern of the case that a deceleration stop command is inputted during acceleration. Also, f2 is a frequency at a point in time when a deceleration stop command is inputted in the operation pattern C, and td2 is deceleration time calculated by expression (1).
td2=(f2/fstd)xc3x97td1xe2x80x83xe2x80x83expression (1)
The deceleration time td2 is calculated by expression (1) and in the case of linear deceleration, a gradient of deceleration becomes constant and in the case of S-shaped curve deceleration, the gradient of deceleration does not necessarily become constant since a deceleration pattern is again recalculated on the basis of the deceleration time td2 calculated by expression (1) and the operating frequency f2 at the time of deceleration.
Also, in the drawing, an example of an S-shaped curve adjustable speed pattern for smoothing a change in speed at the time of start and stop was shown. a11 and a12 are points in time when a deceleration stop command is inputted, and b11, c11 and d11 are way points of S-shaped curve deceleration in the operation pattern B, and b12, c12 and d12 are way points of S-shaped curve deceleration in the operation pattern C. A range between a11 and b11, a range between c11 and d11, and a range between a12 and b12, a range between c12 and d12 are curve deceleration intervals in the S-shaped curve adjustable speed patterns. Also, d11 and d12 are points in time of completion of the S-shaped curve deceleration, and e11 and e12 are points in time when a stop command is inputted after constant speed operation at the frequency fmin at the time of low speed.
Next, deceleration operation patterns of the conventional variable speed apparatus will be described.
In the case of the operation pattern B, when an area between a11 and b11 is set to Sab11 and an area between b11 and c11 is set to Sbc11 and an area between c11 and d11 is set to Scd11 and a moving distance at the time of deceleration from a point a11 in time of deceleration start to a point d11 in time of deceleration completion is set to Sad11, the moving distance Sad11 at the time of deceleration in the case of the operation pattern B becomes expression (2).
Sad11=Sab11+Sbc11+Scd11xe2x80x83xe2x80x83expression (2)
Also, in the case of the operation pattern C, when an area between a12 and b12 is set to Sab12 and an area between b12 and c12 is set to Sbc12 and an area between c12 and d12 is set to Scd12 and a moving distance at the time of deceleration from a point a12 in time of start to a point d12 in time of deceleration completion is set to Sad12, the moving distance Sad12 at the time of deceleration in the case of the operation pattern C becomes expression (3).
Sad12=Sab12+Sbc12+Scd12xe2x80x83xe2x80x83expression (3)
Here, when the moving distance Sad11 at the time of deceleration in the case of the operation pattern B in which the deceleration stop command is inputted during operation at the adjustable speed reference frequency fstd is compared with the moving distance Sad12 at the time of deceleration in the case of the operation pattern C in which the deceleration stop command is inputted during acceleration, it becomes fstd greater than f2 and further td1 greater than td2 in order to keep a gradient of deceleration constant, so that it becomes Sad11 greater than Sad12.
FIG. 9 is a diagram showing an operation pattern of an elevator. In the drawing, the axis of abscissa is a position and shows stop positions of the first floor, second floor, third floor, fourth floor and fifth floor, and the axis of ordinate is a speed and fmax is the maximum frequency and fmin is the frequency at the time of low speed. Also, h2, h3, h4 and h5 are command positions of a deceleration stop command for making a stop in stop positions of the second floor, third floor, fourth floor and fifth floor at the time of rise. In an operation pattern at the time of fall, a direction differs but it becomes the similar movement, so that only the operation pattern at the time of rise was shown in the drawing.
In the elevator, generally, it is constructed so that sensors are mounted in an elevation passage of the elevator and a pass of a cage is detected to output a deceleration stop command. Deceleration stop command input positions (h2, h3, h4 and h5 in the drawing) which become points in time of this deceleration stop command are determined by a system of the elevator and for example, in the case of moving from the first floor to the third floor through fifth floor, the deceleration stop command is inputted during operation (h3, h4, h5) at the maximum frequency fmax, but in the case of moving from the first floor to the second floor, the deceleration stop command is inputted during acceleration (h2) (movement from the second floor to the third floor, movement from the third floor to the fourth floor and movement from the fourth floor to the fifth floor are also similar).
As described above, in the elevator, in order to make a stop in a stop position of each floor with accuracy, a moving distance at the time of deceleration from the deceleration start to the deceleration completion needs to be kept constant regardless of an operating frequency at a point in time of a deceleration stop command input, but when the conventional variable speed apparatus for decelerating by the deceleration time td2 calculated by multiplying the reference deceleration time td1 by a ratio between the operating frequency at the time of the deceleration stop command input and the adjustable speed reference frequency fstd is used in the case that the operating frequency at the time of the deceleration stop command input is different from the adjustable speed reference frequency fstd, there was a problem that the moving distance at the time of deceleration changes depending on the operating frequency at the point in time of the deceleration stop command input.
Also, in order to make a stop in a constant position regardless of an operating speed at a point in time when the deceleration stop command is inputted, by lengthening time for performing constant speed operation at the frequency fmin at the time of low speed or lengthening deceleration time more than the deceleration time td2 calculated by multiplying the reference deceleration time td1 by a ratio between the operating frequency at the time of the deceleration stop command input and the adjustable speed reference frequency fstd, the moving distance at the time of deceleration can be adjusted, but in this case, there was a problem that operating time at low speed becomes long.
Also, even when the S-shaped curve adjustable speed pattern for smoothing a change in speed at the time of start and stop is adopted, in the case that the deceleration stop command is inputted during acceleration, there was a problem that switching from linear acceleration to S-shaped curve deceleration is performed and a shock becomes large.
This invention is implemented to solve the problems described above, and a first object is to obtain a control method at the time of deceleration stop of a variable speed apparatus capable of making a stop in a constant position even when a deceleration stop command is inputted during acceleration.
Also, a second object is to obtain a control method at the time of deceleration stop of a variable speed apparatus capable of smoothly performing switching of speed change to deceleration when a deceleration stop command is inputted during acceleration.
A variable speed apparatus of this invention is constructed so that in a variable speed apparatus having a converter part for converting AC electric power into DC electric power, a smoothing capacitor for smoothing a DC voltage converted by this converter part, an inverter part for converting the DC electric power into AC electric power of a variable frequency, a variable voltage, and a control part for controlling the inverter part so as to make a deceleration stop after decelerating to a frequency at the time of low speed by deceleration time calculated by multiplying preset reference deceleration time by a ratio between an operating frequency at the time of deceleration stop command input and an adjustable speed reference frequency when a deceleration stop command is inputted, the control part comprises constant speed operating frequency calculation means for calculating a first constant speed operating frequency for performing constant speed operation when the deceleration stop command is inputted during acceleration, and constant speed operating time calculation means for calculating first constant speed operating time by the first constant speed operating frequency in order to equalize a moving distance at the time of deceleration from deceleration start to deceleration completion in the case that the deceleration stop command is inputted during acceleration to a moving distance at the time of deceleration from deceleration start to deceleration completion in the case that the deceleration stop command is inputted during operation at the adjustable speed reference frequency, and when the deceleration stop command is inputted during acceleration, operation is performed at the first constant speed operating frequency by the first constant speed operating time and then deceleration is performed to the frequency at the time of low speed by deceleration time calculated by multiplying the reference deceleration time by a ratio between the first constant speed operating frequency and the adjustable speed reference frequency.
Also, the control part comprises constant speed operating frequency correction means for calculating a second constant speed operating frequency for operating by constant speed operating holding time when the first constant speed operating time is longer than the constant speed operating holding time preset, and it is constructed so that when the deceleration stop command is inputted during acceleration and the first constant speed operating time calculated by the constant speed operating time calculation means is longer than the constant speed operating holding time preset, acceleration is further continued to the second constant speed operating frequency and operation is performed at the second constant speed operating frequency by the constant speed operating holding time and then deceleration is performed to the frequency at the time of low speed by deceleration time calculated by multiplying the reference deceleration time by a ratio between the second constant speed operating frequency and the adjustable speed reference frequency.
Also, the control part comprises deceleration time shortening means for determining the first constant speed operating time calculated by the constant speed operating time calculation means and shortening deceleration time calculated by multiplying the reference deceleration time by a ratio between the first constant speed operating frequency and the adjustable speed reference frequency in order to equalize a moving distance at the time of deceleration from deceleration start to deceleration completion in the case that the deceleration stop command is inputted during acceleration to a moving distance at the time of deceleration from deceleration start to deceleration completion in the case that the deceleration stop command is inputted during operation at the adjustable speed reference frequency when the first constant speed operating time becomes minus.